Influence of electroless nickel plating on I–V characteristics and its implications for reliability in ZnO-based ceramic varistors

A comparison experiment was designed and carried out to study the influence of electroless nickel plating on ZnO-based ceramic varistors. It was found that the influence was not caused by permeation of the plating solution; the influence was directly related to nickel deposition. It is proposed that adsorbed hydrogen atoms generated in electroless plating can diffuse into ZnO ceramic varistors and undergo a reduction reaction with them, which result in a substantial increase in the leakage current of the varistors. Some implications for the influence of electroplating on I–V characteristics and for the long-term degradation of ZnO varistors are also discussed, in which much attention is paid to the reduction reaction of atomic hydrogen generated by electrolysis of water.